Nippon Dynawave Packaging has released its first detailed account of the May 26th white liquor tank failure that killed 11 workers and injured many more.

According to the report given to the Washington Department of Ecology, the company says roughly 900,000 gallons of the high-pH material spilled from the storage tank when it failed. The collapse also led to a fire main nearby rupturing, which caused water to shoot out, spreading the chemical over roughly 12 acres of the mill site.

They estimate about 3,500 gallons of white liquor reached the Columbia River, along with up to 160,000 gallons that entered a nearby drainage ditch before crews stopped the flow.

Employees on site took immediate action to contain the spill, limiting environmental damage. They said they handled the emergency as well as they could under the circumstances.

The report does not identify what may have caused the tank to fail. The incident remains under investigation by both the Washington Department of Labor & Industries and the U.S. Chemical Safety Board.